DESCRIPTION: Despite an increasingly detailed picture of the organization of neural circuits in visual cortex, we are still far from understanding the rules that relate these complex patterns of connections to the response properties of individual neurons. The proposed experiments focus on a fundamental property exhibited by many visual cortical neurons--selectivity for direction of motion. Direction selective neurons respond vigorously to movement of an appropriately oriented edge in one direction across their receptive field, and weakly, if at all, to movement in the opposite direction. The goal of this grant is to determine whether specificity in the modular and topographic arrangement of intracortical connections plays a role in shaping the direction selective responses of cortical neurons. These experiments are made possibly by the recent demonstration of a systematic map of direction preference in area 17 of the ferret. Optical imaging of intrinsic signals will be used to visualize the map of direction preference in area 17, and a combination of anatomical tracing techniques and in vitro tissue slice experiments will be used to assess the spatial arrangement of excitatory and inhibitory inputs to populations of neurons with known direction preference. These experiments should provide new insights into the functional organization of local circuits in visual cortex-- information that is crucial for understanding the neural basis of visual perception.